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Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Prof. Dr. Bayram Yılmaz Faculty of Medicine Faculty of Medicine Department of Physiology Department of Physiology YEDİTEPE UNIVERSITY
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Page 1: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Parathyroid Hormone, Calcitonin,

Calcium and Phosphate Metabolism,

Vitamin D and Bone

Prof. Dr. Bayram YılmazProf. Dr. Bayram Yılmaz

Faculty of MedicineFaculty of Medicine

Department of PhysiologyDepartment of Physiology YEDİTEPE UNIVERSITY

Page 2: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

• SkeletonSkeleton

* * Bone tissueBone tissue

Page 3: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Regulation of calcium and phosphate levels in the Regulation of calcium and phosphate levels in the extracellular fluid and plasmaextracellular fluid and plasma

Extracellular fluid calcium concentration normally is regulated very Extracellular fluid calcium concentration normally is regulated very

precisely.precisely.

Normal plasma value is about 9.4 mg/dlNormal plasma value is about 9.4 mg/dl

Hypercalcemia, progressive depression of the nervous systemHypercalcemia, progressive depression of the nervous system

Hypocalcemia, increased excitability of the nervous systemHypocalcemia, increased excitability of the nervous system

Only about 0.1% of total body calcium is found in the extracellular Only about 0.1% of total body calcium is found in the extracellular

fluid, about 1 % in the cells and the rest is stored in the bonesfluid, about 1 % in the cells and the rest is stored in the bones

Page 4: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Calcium in the Plasma and Interstitial FluidCalcium in the Plasma and Interstitial Fluid

The calcium in the plasma is present in three forms:The calcium in the plasma is present in three forms:

1)1) About 41% of the calcium is combined with the plasma About 41% of the calcium is combined with the plasma

proteins and in this form is indiffusible thorugh the capillary proteins and in this form is indiffusible thorugh the capillary

membranemembrane

2)2) About 9% of the calcium is diffusible through the capillary About 9% of the calcium is diffusible through the capillary

membrane but is combined with anionic substances of the membrane but is combined with anionic substances of the

plasma and interstitial fluid (such as citrate and phosphate)plasma and interstitial fluid (such as citrate and phosphate)

3)3) The remaining 50% of the calcium in the plasma is both The remaining 50% of the calcium in the plasma is both

diffusible and ionizeddiffusible and ionized

Page 5: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Calcium in the Plasma and Interstitial FluidCalcium in the Plasma and Interstitial Fluid

Page 6: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Inorganic phosphate in the extracellular fluidsInorganic phosphate in the extracellular fluids

About 85% of the body phosphate is found in the About 85% of the body phosphate is found in the bones; 14-15 % in the cells and less than 1% in the bones; 14-15 % in the cells and less than 1% in the extracellular fluidextracellular fluid

Inorganic phosphate in the plasma is mainly in two Inorganic phosphate in the plasma is mainly in two

forms:forms: HPOHPO44

-

HH22POPO44-

The average total quantity of inorganic phosphorus for The average total quantity of inorganic phosphorus for both ions is about 4 mg/dlboth ions is about 4 mg/dl

Page 7: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Non-bone physiologic effects of altered calcium Non-bone physiologic effects of altered calcium and phosphate concentrations in the body fluidsand phosphate concentrations in the body fluids

Changing the level of phosphate in the extracellular Changing the level of phosphate in the extracellular fluid from far below normal or two or three times normal fluid from far below normal or two or three times normal does not cause major immediate effects on the bodydoes not cause major immediate effects on the body

In contrast, even a slight increase or decrease of In contrast, even a slight increase or decrease of calcium ion in the extracellular fluid can cause extreme calcium ion in the extracellular fluid can cause extreme immediate physiologic effects.immediate physiologic effects.

Hypocalcemia causes nervous system excitement and Hypocalcemia causes nervous system excitement and tetany. Increased permeability of neurons to sodium tetany. Increased permeability of neurons to sodium ionsions

Hypercalcemia depresses nervous system and muscle Hypercalcemia depresses nervous system and muscle activity. These effects become marked as the calcium activity. These effects become marked as the calcium level rises above 15 mg/dllevel rises above 15 mg/dl

Page 8: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Absorption and Excretion of Calcium and Absorption and Excretion of Calcium and PhosphatePhosphate

Intestinal absorption and fecal excretion of calcium and Intestinal absorption and fecal excretion of calcium and phosphatephosphate

Renal excretion of calcium and phosphateRenal excretion of calcium and phosphate Approximately 10% (100 mg/day) of the ingested Approximately 10% (100 mg/day) of the ingested

calcium is excreted in urine calcium is excreted in urine Normally, the renal tubules reabsorb 99% of the filtered Normally, the renal tubules reabsorb 99% of the filtered

calcium, and only 100 mg/day is excreted in urinecalcium, and only 100 mg/day is excreted in urine

Renal phosphate excretion is controlled by an over-flow Renal phosphate excretion is controlled by an over-flow mechanism, when phosphate level is below 1 mmol/lt, mechanism, when phosphate level is below 1 mmol/lt, all phosphate in the glomerular filtrate is reabsorbed…all phosphate in the glomerular filtrate is reabsorbed…

Page 9: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Absorption and Excretion of Calcium and PhosphateAbsorption and Excretion of Calcium and Phosphate

Page 10: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Bone and its relation to extracellular calcium and Bone and its relation to extracellular calcium and phosphatephosphate

Organic matrix of the bone:Organic matrix of the bone: 90-95% collagen fibers, and the remaining 90-95% collagen fibers, and the remaining is homogenous gelatinous medium called ground substanceis homogenous gelatinous medium called ground substance

The ground substance is composed of extracellular fluid plus The ground substance is composed of extracellular fluid plus proteoglycans, especially chondroitin sulfate and hyaluronic acid proteoglycans, especially chondroitin sulfate and hyaluronic acid

Bone salts:Bone salts: The crystalline salts deposited in the organic matrix of the The crystalline salts deposited in the organic matrix of the bone are composed principally of calcium and phosphate.bone are composed principally of calcium and phosphate.

Hydroxyapatite = collagen + Ca(PO4)2 + OH + bicarbonate

Metals, radioactive and toxic substances can also be deposited in the Metals, radioactive and toxic substances can also be deposited in the bonebone

Page 11: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Precipitation and absorption of calcium and phosphate in Precipitation and absorption of calcium and phosphate in bonebone

Concentrations of calcium and phosphate in extracellular fluid are Concentrations of calcium and phosphate in extracellular fluid are greater than those required to cause precipitation of hydroxyapatite greater than those required to cause precipitation of hydroxyapatite

Role of inhibitors: pyrophosphateRole of inhibitors: pyrophosphate

Mechanism of bone calcification: The initial stage in bone production Mechanism of bone calcification: The initial stage in bone production is secretion of collagen molecules and the ground substance is secretion of collagen molecules and the ground substance (mainly proteoglycans) by the osteoblasts(mainly proteoglycans) by the osteoblasts

Formation of osteoid…Formation of osteoid…

Importance of amorphous salts that are not converted in Importance of amorphous salts that are not converted in hydroxyapatite: fall in extracellular calcium and reabsorption of hydroxyapatite: fall in extracellular calcium and reabsorption of amorphous compoundsamorphous compounds

Precipitation of calcium in nonosseous tissues under abnormal Precipitation of calcium in nonosseous tissues under abnormal conditions: formation of arteriosclerosis, precipitation in blood clots.conditions: formation of arteriosclerosis, precipitation in blood clots.

Page 12: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Calcium exchange between bone and extracellular fluidCalcium exchange between bone and extracellular fluid

Importance of exchangeable calcium; a rapid buffering Importance of exchangeable calcium; a rapid buffering mechanismmechanism

Deposition of bone by the osteoblastsDeposition of bone by the osteoblasts

Absorption of bone – function of the osteoclastsAbsorption of bone – function of the osteoclasts

Bone deposition and absorption are normally in equlibriumBone deposition and absorption are normally in equlibrium

Value of continual bone remodelingValue of continual bone remodeling

Control of the rate of bone deposition by bone “stress”Control of the rate of bone deposition by bone “stress”

Repair of a fracture activates osteoblastsRepair of a fracture activates osteoblasts

Page 13: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.
Page 14: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

A coronal section of

bone tissue

Page 15: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

RANK: Osteoclast procursor cells produce a surface receptor protein

RANK Ligand

Ostaoblasts produce osteoprotegerin which interferes with RANKL

Page 16: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Vitamin DVitamin D

Vitamin D has a potent effect to increase calcium absorption from Vitamin D has a potent effect to increase calcium absorption from the intestinal tractthe intestinal tract

Vitamin D itself is not the active substanceVitamin D itself is not the active substance It must first be converted through a succession of reactions in the It must first be converted through a succession of reactions in the

liver and kidneys to the final active product; 1,25-liver and kidneys to the final active product; 1,25-dihydroxycholecalciferoldihydroxycholecalciferol

Cholecalciferol (Vitamin D3) is formed in the skin: UV and 7-Cholecalciferol (Vitamin D3) is formed in the skin: UV and 7-dehydroxycholesteroldehydroxycholesterol

Cholecalciferol that we ingest in foodCholecalciferol that we ingest in food

Vitamin D is lipid soluble and can be stored in fat tissueVitamin D is lipid soluble and can be stored in fat tissue

Page 17: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Synthesis and Functions of 1,25-dihydroxycholecalciferol

Page 18: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Calcium ion concentration controls the formation of

1,25-dihydroxycholecalciferol

Formation of Formation of 1,25-dihydroxycholecalciferol is controlled

inversely proportional to plasma levels of calcium

When plasma calcium levels rise, parathyroid hormone When plasma calcium levels rise, parathyroid hormone

secretion is inhibited, conversion of 25-hidroxycalciferol secretion is inhibited, conversion of 25-hidroxycalciferol

to 1,25-dihydroxycholecalciferol is prevented to 1,25-dihydroxycholecalciferol is prevented

Instead, Vitamin D is converted to an inactive form, Instead, Vitamin D is converted to an inactive form,

24,25-dihydroxycholecalciferol24,25-dihydroxycholecalciferol

Page 19: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Calcium ion concentration controls the formation of

1,25-dihydroxycholecalciferol

Page 20: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Synthesis and Functions of 1,25-dihydroxycholecalciferol

Page 21: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Actions of Vitamin D

Hormonal effect of vitamin D to promote intestinal calcium Hormonal effect of vitamin D to promote intestinal calcium

absorptionabsorption It does this by increasing formation of a calcium-binding protein in the It does this by increasing formation of a calcium-binding protein in the

intestinal epithelial cellsintestinal epithelial cells

Vitamin D promotes phosphate absorption by the intestinesVitamin D promotes phosphate absorption by the intestines

Vitamin D decreases renal calcium and phosphate excretionVitamin D decreases renal calcium and phosphate excretion

Effect of Vitamin D on bone and its relation to parathyroid Effect of Vitamin D on bone and its relation to parathyroid

hormone activityhormone activity Vitamin D in smaller quantities promotes bone calcification, whereas in Vitamin D in smaller quantities promotes bone calcification, whereas in

extreme quantities causes bone absorptionextreme quantities causes bone absorption

In the absence of Vit D, bone resoptive action of PTH is greatly reducedIn the absence of Vit D, bone resoptive action of PTH is greatly reduced

Page 22: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

PARATHYROID HORMONE (PTH)PARATHYROID HORMONE (PTH)

Physiologic anatomy of the parathyroid glandsPhysiologic anatomy of the parathyroid glands

The chief cells in the parathyroid glands secrete PTHThe chief cells in the parathyroid glands secrete PTH

Chemistry of parathyroid hormone: proteinChemistry of parathyroid hormone: protein

Page 23: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

ParatParathyroid Glandshyroid Glands

Page 24: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

ParatParathyroid Glandshyroid Glands

Page 25: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

ParatParathyroid Glands and Histologyhyroid Glands and Histology

Page 26: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Effect of PTH on calcium and phosphate

concentrations in the extracellular fluid

PTH increases plasma calcium concentrationsPTH increases plasma calcium concentrations

1- It increases calcium and phosphate absorption in the bone1- It increases calcium and phosphate absorption in the bone

2- With the fast action of PTH, it decreases renal excretion of 2- With the fast action of PTH, it decreases renal excretion of

calciumcalcium

Rapid phase of calcium and phosphate absorption: OsteolysisRapid phase of calcium and phosphate absorption: Osteolysis

Slow phase of bone absorption and calcium phosphate release: Slow phase of bone absorption and calcium phosphate release:

Activation of the osteoclastsActivation of the osteoclasts

Osteoclasts do not themselves have membrane receptors for PTHOsteoclasts do not themselves have membrane receptors for PTH

Page 27: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

PTH decreases calcium excretion and increases PTH decreases calcium excretion and increases phosphate excretion by the kidneysphosphate excretion by the kidneys

PTH causes rapid loss of phosphate in urine, by decreasing its PTH causes rapid loss of phosphate in urine, by decreasing its

tubular reabsorptiontubular reabsorption

In contrast, PTH increases tubular reabsorption of calciumIn contrast, PTH increases tubular reabsorption of calcium

The increased calcium absorption occurs mainly in the The increased calcium absorption occurs mainly in the

late distal tubule and collecting tubuleslate distal tubule and collecting tubules

PTH increases intestinal absorption of calcium and phosphatePTH increases intestinal absorption of calcium and phosphate

Role of Vitamin DRole of Vitamin D

Page 28: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Control of PTH Secretion by CalciumControl of PTH Secretion by Calcium

PTH secretion is controlled by plasma concentrations of PTH secretion is controlled by plasma concentrations of

calciumcalcium

Increased activity of parathyroid glands in pregnancy and Increased activity of parathyroid glands in pregnancy and

lactationlactation

Conditions that increase plasma calcium levels above normal Conditions that increase plasma calcium levels above normal

cause decreased activity and reduced size of the parathyroid cause decreased activity and reduced size of the parathyroid

glandsglands

Page 29: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

CALCITONINCALCITONIN

Calcitonin is a peptide hormone secreted by parafollicular (C type) Calcitonin is a peptide hormone secreted by parafollicular (C type)

cells in the thyroid glandcells in the thyroid gland

High plasma calcium concentrations increase calcitonin releaseHigh plasma calcium concentrations increase calcitonin release

In turn, calcitonin reduces plasma calcium concentrationsIn turn, calcitonin reduces plasma calcium concentrations1- The immediate effect is to decrease the absorptive activities of the osteoclasts 1- The immediate effect is to decrease the absorptive activities of the osteoclasts

and possibly the osteolytic effect of the osteolytic membraneand possibly the osteolytic effect of the osteolytic membrane

2- The second and more prolonged effect of calcitonin is to decrease the 2- The second and more prolonged effect of calcitonin is to decrease the

formation of new osteoclastsformation of new osteoclasts

Calcitonin has a weak effect on plasma calcium concentration in the Calcitonin has a weak effect on plasma calcium concentration in the

adult humanadult human

Page 30: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Control of calcium concentrations in the extracellular fluid

1- The first line of defense: Fuffer function of exchangable calcium in the bone

2- The second line of defense: Hormonal control

Page 31: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Regulation of PTH SecretionRegulation of PTH Secretion

Page 32: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

HYPOPARATHYROIDISMHYPOPARATHYROIDISM

When the parathyroid glands do not secrete sufficient PTH, When the parathyroid glands do not secrete sufficient PTH,

osteocytic reabsorption of exchangable calcium decreases and the osteocytic reabsorption of exchangable calcium decreases and the

osteoclasts become almost totally inactiveosteoclasts become almost totally inactive

Hypoparathyroidism causes hypocalcemiaHypoparathyroidism causes hypocalcemia

In its treatment, Vitamin D and calcium are administeredIn its treatment, Vitamin D and calcium are administered

Hypoparathyroidism is usually not treated with PTH administrationHypoparathyroidism is usually not treated with PTH administration

Page 33: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

PRIMARY HYPERPARATHYROIDISM The cause of primary hyperparathyroidism is usually a tumor of one of the The cause of primary hyperparathyroidism is usually a tumor of one of the

parathyroid glandsparathyroid glands

Bone disease in hyperparathyroidism: In severe hyperparathyroidism, Bone disease in hyperparathyroidism: In severe hyperparathyroidism,

increased osteoclastic reabsorption far exceeds osteoblastic depositionincreased osteoclastic reabsorption far exceeds osteoblastic deposition

And the bone may be eaten away entirelyAnd the bone may be eaten away entirely

In addition to absorption of the old bones, osteoblastic activity to form new In addition to absorption of the old bones, osteoblastic activity to form new

bone also increases bone also increases

When osteoblasts become active, they secrete large quantities of alkaline When osteoblasts become active, they secrete large quantities of alkaline

phosphatasephosphatase

Effects of hypercalcemiaEffects of hypercalcemia

Parathyroid poisoning and metastatic calcificationParathyroid poisoning and metastatic calcification

CaHPO4 crystals become deposited in the alveoli of the lungs, CaHPO4 crystals become deposited in the alveoli of the lungs,

kidneys, thyroid gland, arteries and stomachkidneys, thyroid gland, arteries and stomach

Formation of kidney stones in hyperparathyroidismFormation of kidney stones in hyperparathyroidism

Page 34: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

SECONDARY HYPERPARATHYROIDISMSECONDARY HYPERPARATHYROIDISM

In secondary hyperparathyroidism, high levels of PTH occur as a In secondary hyperparathyroidism, high levels of PTH occur as a

compensation for hypocalcemia rather than a primary tumor of the compensation for hypocalcemia rather than a primary tumor of the

parathyroid glandparathyroid gland

It can be caused by Vit D deficiency or failure to form active Vit D in chronic It can be caused by Vit D deficiency or failure to form active Vit D in chronic

renal diseaserenal disease

Rickets – Vitamin D deficiencyRickets – Vitamin D deficiency

Mainly occurs in childrenMainly occurs in children

It results from calcium or phosphate deficiency in the extracellular fluidIt results from calcium or phosphate deficiency in the extracellular fluid

Usually caused by vitamin D deficiencyUsually caused by vitamin D deficiency

Page 35: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

SECONDARY HYPERPARATHYROIDISMSECONDARY HYPERPARATHYROIDISM

Rickets:Rickets:

Plasma concentration of calcium and phosphate decrease in Rickets: Plasma concentration of calcium and phosphate decrease in Rickets:

The plasma calcium concentration is rickets is only slightly The plasma calcium concentration is rickets is only slightly

depressed, but the level of phosphate is greatly decreaseddepressed, but the level of phosphate is greatly decreased

Rickets weakens bonesRickets weakens bones

Tetany in ricketsTetany in rickets

Treatment of rickets:Treatment of rickets: Supplying adequate calcium and phosphate in the dietSupplying adequate calcium and phosphate in the diet

Administering large amount of Vit DAdministering large amount of Vit D

Page 36: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

RicketsRickets►Deficiency of Vit D in Deficiency of Vit D in

childhoodchildhood

Lack of sun exposureLack of sun exposure

Deficiency in dietDeficiency in diet

► Decreased plasma calciumDecreased plasma calcium

► Increased PTH secretionIncreased PTH secretion

► Increased bone resorptionIncreased bone resorption

O O oror X X legslegs

Page 37: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

SECONDARY HYPERPARATHYROIDISMSECONDARY HYPERPARATHYROIDISM

Osteomalacia (adult rickets) Osteomalacia (adult rickets)

Adults seldom have a dietary deficiency of vit D or calciumAdults seldom have a dietary deficiency of vit D or calcium

Serious deficiency of vit D or calcium occasionally occur as a Serious deficiency of vit D or calcium occasionally occur as a

result of steatorrhea (failure to absorb fat)result of steatorrhea (failure to absorb fat)

Osteomalacia caused by renal rickets: Osteomalacia caused by renal rickets:

Page 38: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

OSTEOPOROSISOSTEOPOROSIS

Osteoporosis: decreased bone matrixOsteoporosis: decreased bone matrix

Osteoporosis is the most common of all bone diseases in Osteoporosis is the most common of all bone diseases in

adults. Most common causes are:adults. Most common causes are:

1- Inactivity (lack of physical stress)1- Inactivity (lack of physical stress)

2- Malnutrition, lack of protein in diet2- Malnutrition, lack of protein in diet

3- Deficiency of Vit C (reduced osteoblastic activity)3- Deficiency of Vit C (reduced osteoblastic activity)

4- In older ages, markedly decreased growth hormone and other 4- In older ages, markedly decreased growth hormone and other

factorsfactors

5- Cushing Syndrome5- Cushing Syndrome

6- Reduced secretion of estrogen in menopause6- Reduced secretion of estrogen in menopause

Page 39: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.
Page 40: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

Estrogen and OsteoporosisEstrogen and Osteoporosis

Role of cytokines in the bone tissueRole of cytokines in the bone tissue Bone resorption increasing effectBone resorption increasing effect

Estrogen

IL-1, IL-6, TGF- and TNF-

Bone resorption

+

-

Page 41: Parathyroid Hormone, Calcitonin, Calcium and Phosphate Metabolism, Vitamin D and Bone Prof. Dr. Bayram Yılmaz Faculty of Medicine Department of Physiology.

PHYSIOLOGY OF TEETH


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